Once you have Crossover on your Mac, you can double click any NWC setup program and install it into a new bottle. When you double click the setup program, the Crossover Software Installer box should open to allow you to configure how it should be installed. There are also CrossTie files available:

At this point, simply click the Install button to complete the process. The NWC Viewer program will appear in the Crossover Programs menu, as well as in the Finder via your personal Applications, Crossover folder. Here it is running in OS X Mavericks:

If you have other Windows software and want full Windows compatibility, then you may want to use a virtualization solution with one of these programs (in alphabetical order):

When preparing to use the Rhythm Tracks for NWC App on a Mac, a virtual MIDI synthesizer is also needed before you can hear the pattern loops during play back. In order to create the virtual synthesizer, you will need a program called AU Lab.